Digital images can be color (e.g., made up of red, green, and blue components) or black and white (e.g., grayscale). Many image editing applications have the ability to convert color images to black and white (grayscale) images. Such image editing applications generate a luminance (or brightness) for each pixel based on a weighted sum of the levels of green, blue, and red in the pixel. However, most of these applications have pre-set weights for their conversion functions. Such applications do not provide an option for the user to alter the weights for the conversion functions. Some image editing applications do allow the user to adjust the weights for conversion functions. However, such prior art image editing applications give the user too many options by allowing any of the weights to be set independently. The results of setting all three weights to arbitrary levels are often poor. Therefore, there is a need in the art for an image editing application that gives a user some control over grayscale conversion, but constrains the weighting to values that produce acceptable results.